A. Technical Field
The present invention relates to power supplies, and more particularly, to systems, devices, and methods of controlling DC/DC multi-phase constant on time switching regulators.
B. Background of the Invention
Multiphase DC/DC converters are used in consumer electronics applications to supply power to CPUs for notebook, servers, and in many other applications that require high DC/DC converter bandwidth, low inductor ripple current, reduced inductor size, reduced output capacitor decoupling requirements, and high output voltage accuracy when subjected to load current variations. Conventional constant on time architectures or adaptive on time architectures are not widely used for multiphase switching regulators with more than three phases, because compared to other solutions, these kinds of regulators suffer greatly from duty cycle limitations that disproportionally worsen as the number of phases is increased. At any given operating frequency, the duty cycle is limited by 1/Nph, where Nph represents the number of phases. The maximum duty cycle in existing applications is typically 25 percent, such that the maximum number of phases is three, which corresponds to a theoretical maximum duty cycle of 33 percent.
Conventional constant on time and adaptive on time multiphase DC/DC converters are typically implemented with single error amplifiers and single on time generators that generate non-overlapping consecutive phases. In fact, multi-phase architectures that use a single on time generator are incapable of generating overlapping phases for a constant load. Nonoverlapping consecutive phases are generated by blanking, in a present cycle, the on time pulse of the following cycle by a minimum off time that must expire before the on time pulse can be triggered. Unfortunately, the off time delay restriction may significantly slow down transient response time, especially for heavy load transients. In addition, the minimum off time reduces the theoretical maximum duty cycle limit of 1/Nph.
One possible approach to avoid the strict requirement of nonoverlapping multiple phases is to employ one error amplifier and one corresponding on time generator for each phase. However, using multiple error amplifiers greatly increases the complexity of the converter, for example, due to the difficulty to ensure proper phase shift between phases, which renders this approach rather impractical.
What is needed are tools for switching regulator designers to overcome the above-described limitations and to meet the new demands of the marketplace.